Short of asking the involved parties, the best you can do is to follow some of the PHP discussions on this topic, such as this one http://www.mail-archive.com/internals@lists.php.net/msg59731...

The first use-case for finally involved locking database tables, and then unlocking them in the finally clause. It would be pretty bad, if you could not guarantee the unlock would happen. So one would hope that has been properly taken care of :-)